Introduction to Peakvue

Objectives

To Understand:

1. What Peakvue Is!

2. How it Works! 3. Filter Options
Types of filters available Calculating the correct filter setting Filter Guidelines

4. Peakvue Data
Spectrums and Waveforms
Diagnosing Faults

5. Peakvue Versus Demodulation Techniques 6. Acquiring Peakvue Data using the 2120A

What is Peakvue

What is Peakvue?
Peakvue is a technology unique to CSI and means Peak Value Such as the Peak Value of an impact generated by a bearing defect in a time waveform - (True Peak Value) If you have a 21XX analyzer you have the capability to acquire Peakvue Data

The True Peak Value is obtained by concentrating on Stress Wave Analysis rather than conventional vibration data. These stress waves travel further than conventional vibration signals so a truer indication of fault severity is obtained.

What is Peakvue

What is a Stress Wave? Stress waves accompany metal-metal impacting. These stress waves are short-term (fractional to a few milliseconds) transient events, which introduce a ripple effect on the surface machinery as they propagate away from the initial event.
If you think of a stone being dropped into a pool of water. The stone is the initial impact generated by the fault. The effect of the stone being dropped into the water cause a ripple on the surface of the water which, spreads over a wide area.
Initial Impact

What is Peakvue

If a bearing has a sub-surface defect (early bearing wear), when a rolling element passes over the defect it bends the race slightly and then as the rolling element passes it restores back to its natural state.

This event causes a high frequency (1-50KHz) short duration stress wave. This is what Peakvue detects

How Does It Work?

High Vibration Signal Pass Filter Full Wave Rectify Digital Peak Impact Detection FFT

A comparison can be made of the sampling to show how data is collected through both methods of data acquisition, normal and Peakvue.

How Does It Work?

The diagram below shows sampling of data using normal data collection.
Stress wave- this is missed under normal conditions

Instantaneous Samples

How Does It Work?

The diagram below shows sampling of data using Peakvue data collection.

Stress wave- this is missed under normal conditions

Peakvue Samples

How Does It Work?

Peakvue measures the highest amplitude found in a stress waves (Pk Value) and holds that data The waveform data is then passed through a high pass filter to remove the unwanted, low frequencies
Imbalance, Misalignment, Looseness, resonance etc.

This just leaves us with the high frequency impacting data (Peak) above the machine noise level
The data is then brought back to fundamental frequency. (this allows analysis of the data to be done quicker and easier)

Filters
Types of filter available Filter Calculations Filter Guidelines

Filters Options

One of the key elements in acquiring meaningful peakvue data is the selection of filters Selecting the wrong type of filter will result in poor quality data
To much noise filtered through (the spectrum becomes very noisy) To much is filtered out (The stress wave is not allowed to pass through)

There are two types of filter options in Peakvue, these are:

1. Band Pass Filter

2. High Pass Filter

Each of the filters are designed to remove unwanted data out of the signal at the appropriate levels

Filter Options - High Pass Filter

High Pass Filters remove all frequencies from the data below the filter setting but allow the high frequency stress wave to pass through.

All low frequencies are removed from the input signal

Stress Wave data is allowed to pass through the filter

High Pass Filter

Filter Options - Band Pass Filters

Looks for stress waves within a parameter defined by the filter setting. Frequencies above and below this setting are removed from the data

Data passes through filter Data is filtered out of the signal Data is filtered out of the signal

Filter Selection

To select the correct filter we need to consider the highest operational defect frequency that we want to measure/detect. Then select the next available filter above that frequency

E.g.
Consider a typical motor / pump arrangement. We have:
1 - 4 Pole A.C. Induction Motor 2 - 3 Jaw Coupling 3 - Centrifugal Pump

Typically the highest defect frequency to emit from this machine would be?
1 - BPFI - Bearing Defect

Filter Selection

4 Pole Motor A.C Induction fitted with bearings SKF 6313

Defect Frequencies (Orders)
FTF - 0.384 BSF - 2.037 BPFO - 3.071 BPFI - 4.929

Typically we would want to see the 10th Harmonic of the BPFI

Highest defect frequency:
(BPFI x 10) x Turning Speed (Hz) (4.929 x 10) x 25

1232.3 Hz

We would then select the next available filter setting above the frequency

Available filters

High Pass Filters

Band Pass Filters

500hz
1000hz 2000hz 5000hz 10000hz 20000hz

20hz 150hz
50hz 300hz 100hz 600hz 500hz 1khz

From our previous calculation of 1232Hz, What filter setting would we select?

Note: the meter will only allow you to select the next filter above the specified Fmax.

Filter uses (Band Pass) - Guidelines

Band Pass Filters

20hz 150hz Felt problems on paper machines 50hz 300hz Certain structural resonance excitation, modulation of gearmesh in low speed machinery 100hz 600hz Gearmesh modulation in intermediate speed machinery. 500hz 1khz Gearmesh modulation

Tip: use bandpass filters when the event of interest is the excitation of a structural resonance, or the modulation of known frequencies such as gearmesh.

Filter uses (Highpass) - guidelines

High Pass filters

500hz Low speed machinery having <125hz. Bearing & gearing problems 1000hz Intermediate speed machinery (<2000 rpm) with gear mesh <300hz 2000hz Medium speed machinery (<4000rpm) with gear mesh ,600hz 5000hz Machinery up to 9000rpm and gear mesh to 1500hz, Requires attention be paid to how the sensor is mounted as well as the sensors frequency response. 10000hz High speed machinery with gear mesh up to 3000hz sensor must be permanently mounted with a frequency response of 3db in the 30kHz or higher range. 20000hz High speed machinery with gearmesh up to 6000hz. Sensor must be high frequency and permanently mounted.

Tip: Use highpass filters when the objective is to detect stress waves which are emitted by metal on metal impacting.

Filter Selection - Question

Consider:

Motor running at a speed of 1000RPM

Driving a fan unit via pulley belts Fan Speed is 1350RPM
Motor Bearings = SKF 3095 - BPFI 4.855 Fan Bearings = SKF 6210 - BPFI 5.907

Calculate what Filter setting would be required for both the motor and the fan bearings?
Filters Available:
500 Hz, 1000Hz, 2000Hz, 5000Hz, 10000Hz, 20000Hz. (High Pass)
20-150Hz, 50-300Hz, 100-600Hz, 500-1KHz. (Band Pass)

Filter Selection - Answers

Motor Speed = 1000CPM / 60 = 16.667Hz

Fan Speed = 1350CPM / 60 = 22.5Hz

Motor.
BPFI = 4.855 Defect Frequency = (BPFI x 10) x Turning Speed (Hz) Defect Frequency = (4.855 x 10) x 16.667 Defect Frequency = 809.18 Hz

Filters Available:
500 Hz, 1000Hz, 1000Hz 2000Hz, 5000Hz, 10000Hz, 20000Hz. (High Pass) 20-150Hz, 50-300Hz, 100-600Hz, 500-1KHz. (Band Pass)

Filter Selection - Answers

Motor Speed = 1000CPM / 60 = 16.667Hz

Fan Speed = 1350CPM / 60 = 22.5Hz

Fan
BPFI = 5.907 Defect Frequency = (BPFI x 10) x Turning Speed (Hz) Defect Frequency = (5.907 x 10) x 22.5 Defect Frequency = 1329.07Hz

Filters Available:
500 Hz, 1000Hz, 2000Hz, 2000Hz 5000Hz, 10000Hz, 20000Hz. (High Pass) 20-150Hz, 50-300Hz, 100-600Hz, 500-1KHz. (Band Pass)

Peakvue Data
Spectrums and Waveforms Diagnostics Techniques

Peakvue - Spectrum

Here is a typical Peakvue spectra plot. 2. Units should be acceleration (Very high frequency analysis) 1. Broad band energy - Filtered Noise

3. Amplitude values are low. Severity of fault is not determined in the spectra

This is typically a GOOD spectrum

Peakvue - Spectrum

This is a Peakvue spectrum where high frequency stress waves are being detected 2. Units still in acceleration (Very high frequency analysis)

Notice the Impacts passing through the filtered noise

1. Broad band energy - Filtered Noise

3. Amplitude values are low. Remember severity of fault is not determined in the spectra

This is indication of a fault developing

Peakvue - Waveforms

Waveforms can be confused with spectrums, as the waveform is only plotting the peak value and does not show a full wave.
0 .6 EX 1 A1 - E x am ple 1 -D3P Tail Roll Non D/S P e a kv ue Ana lyz e W av e form 16 -Ma r-01 12 : 03 : 1 4 (P kV ue- HP 50 0 Hz)

2. Peak Value Impacts

0 .5 0 .4

Acceleration in G-s

PK = .05 5 6 LOAD = 1 00 .0 RP M = 80 . RP S = 1 .3 3 PK(+) = .5 5 99 PK(-) = .03 97 CRE S TF= 1 4.2 5

0 .3

0 .2

1. Filtered Noise Level

0 .1

4. Acceleration 0 as default units

-0.1 0 Label: E as y 3 6 Rev olution Num be r 9 12

3. No Peak Negative Value

Peakvue - Diagnostics

Diagnosing a Peakvue spectrum and waveform is not to dissimilar to that of conventional data. However there are a few differences which can be a bit confusing at first, these are:
1. Do not try to locate 1xTurning Speed, as this is low frequency data and will be filtered out.
Turning speed should be entered using the conventional spectral data.

2. Multiple harmonics are often present within a spectrum due to the way peakvue samples the data.
These do not indicate Looseness

3. Spectral amplitudes are always low in amplitude but should not be used to judge severity. Use the spectrum to diagnose the fault. 4. Waveforms indicate the severity of the problem.

Peakvue - Diagnostics

Continued..
5. Ensure the same filter setting is used in both the spectrum and waveform.
Potential faults can be missed or overlooked if different filters are used.

6. Cage Defects show up well in peakvue data and is normally an indication the bearing is under stress. 7. All low frequency faults are removed from the data and will not be seen in a Peakvue spectrum and waveform
Imbalance, Misalignment, Looseness, Resonance - All Gone.

Peakvue - Diagnostics
1.Spectral data indicating a defect at 5.463 Orders
3. Very Slow RPM 2. Impacting also being detected at 0.6G-s

Peakvue - Diagnostics
4.Fault Frequencies Indicate a BPFI Defect

Peakvue Amplitudes Rolling Element Bearings

For machines running between speeds of 900 - 3600RPM recommended guidelines for setting initial warning levels in the Peakvue time - waveform are as follows:

Alert Value Inner Race Outer Race Rolling elements fault Cage frequencies 3.0g's 6.0g's 4.5g's

Fault Value 6.0g's 12.0g's 9.0g's

If evident then the bearing is usually under stress.

Peakvue Amplitudes Rolling Element Bearings

For machines running at speeds <900RPM recommended guidelines for setting initial warning levels in the Peakvue time- waveform are as follows:
7
Levels for concern for machines running below 900 RPM

6 Inner race Amplitude (g's) Outer race Amplitude (g's) Rolling elements Amplitude (g's) 4.4 4.1 3.9 3.3 2.9 2.6 1.9 1.5 0.9 0.7 0.5 1.2 0.9 0.6 1.0 2.0 1.6 1.3 1 2.4 2.2 1.9 2 2.5 3.3 3 2.7 3.7 5.0 5.5 5 4.5 4
Acceleration g's

0.2 0.2 0.1 10 35

0.5 0.4 0.3 75

100

200

300

RPM

400

500

600

700

800

0 900

Peakvue Vs Demodulation

Peakvue Vs Demodulation

What is Demodulation?
This is a technique which concentrates on stress wave analysis, but is not as effective.

How Does it Work?

Demodulation looks for the ringdown that follows an impact, and tries to measure how quickly it fades. In order to do this the Time Waveform has to be manipulated in such away that the waveform data becomes useless Less than 1ms Initial Impact

Ringdown

Peakvue Vs Demodulation

What are the Differences?

Peakvue samples the data much quicker enabling it to catch the very short duration high frequency stress wave. It then holds that Peak Value throughout its parameter. Due to the Analogue filtering system used by Demodulation, results in a delay in response and the stress wave impact is missed

Demodulation registers

Peak Impact Detection registers

Peakvue Vs Demodulation
The Process!
High Pass Filter Low Pass Filter

Standard Demodulation
Full Wave Rectify
Remove

A/D
Converter

DC Bias

FFT

Enveloping Stage

Peak Impact Detection

High Pass Filter Full Wave Rectify Digital

Peak
Impact Detection

FFT

Peakvue Vs Demodulation

Case Study.
Equipment
A conveyor system consisting of six rolls is driven by a motor/gearbox unit (GMU). The motor speed is 1500RPM reduced through the gearbox giving the roller speed to be 98.5RPM

Peakvue Vs Demodulation

Data was collected on each bearing of the conveyor system

Due to the slow speeds Peakvue and Demodulation Filters were both set to 500Hz High Pass using 1600 Lines of Resolution
00 .0 16 .0 7 Max Amp .04 90
0 .0 6 E x1
P v D - E xa mple 1 P v D - E xa mple 1 E x1 -R1 P Rolle r Be a ring Driv e End (18 -De c -0 1) -R1 P Rolle r Be a ring Driv e End 0 .0 5 eS Spe pectrum ctrum Ana lyz e c-01 1 14 14: :1 20: 2:2 36 0 18 -De c-0 .0 450 (Dem od-0 HP 500 0 Hz) Hz ) (P kV ueHP

G-s in G-s Acceleration in PK Acceleration PK PK Acceleration in G-s

0 .0 12 0 .0 5

Direct Comparison Demodulation Spectra Between the Two Peakvue Spectra

PK = .12 .02 9 5 0 .03 38 LOAD = =1 100 00.0 .0 LOAD = 99 97.. RP M = = 1 1.6 .64 2 RP S = 0 .0 2

0 .0 4
0 .0 1

0 .0 08
0 .0 3

Peakvue
0 1 8-Dec -01 1 4: 1 0: 26

0 .0 2 0 .0 04

0 .0 1

Demodulation
1 8-Dec -01 1 4: 1 0: 26 1 00 1nc 00y in Hz Freque Freque nc y in Hz Label: P ea kv ue 5 00 High P as s Dem odulate d Hz 5 00 Hz High P as s 50 50 1 50 1 50 2 00 2 00

0
0 0

Peakvue Vs Demodulation
E x1 P v D - E xa mple 1 -R1 P Rolle r Be a ring Driv e End

P lot S pa n 1 .0

Acceleration in G-s

Demodulation Waveform

1 8-Dec -01 1 4: 22

Peakvue Waveform
-0.2 1 8-Dec -01 1 4: 10

Rev olution Num be r

Acquiring Peakvue Data

Setting up the 2120A Creating a Peakvue AP Set

Setting up the 2120A

Peakvue can be accessed from the Analysis Expert options found among the command keys of the 2120A

There are two ways of acquiring peakvue data within the 2120A
Bearing/Gear Analysis - Peakvue
Preset to acquire Peakvue data based upon the AP set assigned to the machine

User Setup Option

Allows user interface to define their own parameters

Setting up the 2120A

User Set-up Option

Define the Fmax you wish to go to. Remember the Fmax is going to define your filter setting.
0 - 30 KCPM = 500Hz High Pass 30 - 60 KCPM = 1000Hz High Pass 60 - 120 KCPM = 2000Hz High Pass 120v - 300 KCPM = 5000Hz High Pass

Lines of Resolution
These have to be good enough to capture the FTF of a bearing, which would equate to around 15 Revolutions of waveform data.
Number of Revs = Number of lines / Fmax(Orders)
E.g. 800 Lines over an Fmax of 60 Orders = 13.3 Revolutions (Inadequate) 1600 Lines over an Fmax of 60 Orders = 26.6 Revolutions (OK)

Setting up the 2120A

Averages
This has to be set to 1 Average to gain the true peak value.
If you start averaging the data then a stress wave detected in the first average that is not there in the second will lose its true amplitude when averaged together.

Units
The default unit for peakvue is Acceleration. Remember we are trying to detect very high frequency events, well above conventional vibration data. Acceleration accentuates high frequencies.
Sensor units can be used if using an accelerometer, however CSI recommend a minimum mounting of a Rare Earth Magnet for data collection

By using the Page Down Button we can toggle through the pages until we find our Peakvue Options (Page 4 of 4)
We turn Peakvue to Yes The Pre-filter can now be changed to our required HP Setting

Setting up the 2120

Data collection can now commence.

Check the data once collection has finished

Look for:
Impacts in both spectrum and waveform Amplitude levels of the Waveform quality of the data

If a problem is detected you may want to acquire more data with a different filter setting. Remember to store the data once the reading has been taken

At least one Peakvue point should be applied to each critical machine to detect early bearing wear, gearwear or adverse metal to metal contact.
This will need building in the database and adding to the route

Peakvue
Analysis Parameter Setup Mastertrend and RBMware

Peakvue AP Set up I

1. 2.

Open Database Management Select Analysis Parameter

Peakvue AP Set up II
1. Complete the spectrum setup, specifying Fmax, LOR and averages (1). Specify the number of parameters - 2

2.

Peakvue AP Set up III

1. 2. 3.

Check, Use Analog pre-processor Select Peakvue, under the Envelope Demodulator Select the filter setting.

Peakvue AP Set up IV

1.

2.

Uncheck, obtain special time waveform? - As Default units will be acceleration Discard all settings when this is unchecked

Peakvue AP Set up V
1. Complete Analysis Parameter specifications, the most important parameter is the peak to peak waveform parameter. Ensure unit type is acceleration

2.

Gearbox case study

Diagram

M1 M2

G3

G5

G7 G9 G11

G1

G10

G12

G8

G4

G6

Introduction

The above gearbox had been overhauled in the workshop and was on its final test run. A vibration signature was taken to confirm a small knock believed to be coming from the coupling, and prove the gearbox was OK.

The readings were taken using Peakvue and standard Vibration Technology on the corresponding points indicated in the diagram above. The following spectrum where obtained.

Standard Data
The standard spectrum below was taken from G5. Is there a Problem?
M1 M2 G1 G3

G4 G6
G8 G10 G12 G9 G11

G5 G7

PeakVue Data
The Peakvue reading shows distinct energy at 6.941 Hz and multiple harmonics of this which is the running speed of the third shaft. The bottom waveform shows clearly a substantial impacting of up to 12 Gs occurring each revolution.

The fault

The diagram below indicates the location of the suspected gear fault and was diagnosed as possibly a damaged tooth
Faulty Gear M1 G3 G1 G5 G7 G9 G11

M2

G10 G8 G4 G6

G12

When the gearbox was re-stripped and examined a cracked tooth on the gear identified was found.